Sql Miscellaneous — Part 2 MCQs with Explanations

In SQL, the "SELECT ALL" statement is used to select all rows, which is the default behavior of the "SELECT" statement. If the statement "SELECT column1 FROM myTable;" returns 10 rows, then the statement "SELECT ALL column1 FROM myTable;" will also return exactly 10 rows because it selects all rows from the specified column in the table. Option C is the correct choice.

In this statement, you are comparing the SALARY column of each employee with the result of the subquery that selects all SALARY values from the same table. Since the SALARY column is unique, there is no salary greater than ALL the salaries in the same table, including itself. Therefore, the condition SALARY > ALL (SELECT SALARY FROM EMPLOYEE) will always be false for all records, resulting in a count of 0 .

The SQL command used to add data to a database table is INSERT . The INSERT statement is used to insert new rows or records into a table. Option D is the correct choice for adding data to a table in SQL. Options A, B, and C are not typically used for this purpose in SQL.

The join known as an 'inner-join' is also referred to as an Equijoin . An Equijoin is a type of join in SQL that combines rows from two or more tables based on a related column between them, using the equal (=) operator. It selects only the rows for which there is a match in both tables. Option C is the correct choice for the join also known as an 'inner-join.' Options A and B are different types of joins, and Option D states that none of these terms refer to an inner-join.

The result of a SQL SELECT statement is a table. When you execute a SELECT statement in SQL, it retrieves data from one or more tables and presents it as a result set, which is essentially a table of data. This result set can be used for various purposes, such as reporting, analysis, or further processing in your database. Options A, B, and D do not accurately represent the typical result of a SELECT statement in SQL.

In SQL, comparison operators are used to compare values in the WHERE clause to filter rows based on specified conditions. The correct usage of these operators is as follows: Greater than (>): Compares if a value is greater than another. Less than (<): Compares if a value is less than another. The correct SQL syntax for using comparison operators to filter rows where the "age" column is greater than 50 and less than 80 is as shown in "Option B." Let's break down the correct query: SELECT name, course_name: This part of the query specifies the columns to be retrieved in the result. FROM student: It specifies the table from which the data is retrieved. WHERE age > 50 and age < 80: This part specifies the conditions for filtering the rows. It correctly uses the ">" and "<" comparison operators to filter rows where the "age" column is greater than 50 and less than 80. The correct option, therefore, is "Option B."

To select all data from the "student" table where the names start with the letter 'r,' you can use the LIKE operator in SQL. Here's an explanation of each option: Option A: SELECT * FROM student WHERE name LIKE 'r%'; This option selects all rows where the "name" column starts with 'r'. Option B: SELECT * FROM student WHERE name LIKE '%r%'; This option selects all rows where the "name" column contains the letter 'r' anywhere within the name. Option C: SELECT * FROM student WHERE name LIKE '%r'; This option selects all rows where the "name" column ends with the letter 'r'. Option D: SELECT * FROM student WHERE name LIKE '_r%'; This option selects all rows where the "name" column has 'r' as the second letter. Since you want to select names starting with 'r,' the correct query is Option A , which uses 'r%' in the LIKE clause to match names that start with 'r'.

SELECT name FROM staffinfo WHERE salary IN (10000, 25000); This query correctly selects the names of staff members whose salary is either 10,000 or 25,000. The correct answer is Option B because it selects the names of staffs with salaries of 10,000 or 25,000, as required by the question.

To insert values into a table using SQL, you should use the INSERT INTO statement, followed by the table name and the keyword VALUES. The correct syntax is: Option C: INSERT INTO student VALUES ( This option is the correct choice for inserting values into the "student" table. Option A: INSERT student VALUES ( This option is incorrect because it lacks the "INTO" keyword. Option B: INSERT VALUES ( This option is incorrect because it is missing the table name. Option D: INSERT VALUES INTO student ( This option is also incorrect as it has an incorrect order of keywords. So, the correct answer is Option C as it follows the proper syntax for inserting values into the "student" table in SQL.

The type of join that involves joining two or more tables based on a specified column value not equaling a specified column value in another table is known as a NON-EQUIJOIN . In a non-equijoin, the condition for joining is based on inequality or non-equality of values between the columns in different tables. Option A: EQUIJOIN - This type of join matches tables based on the equality of column values and is not relevant to non-equijoin. Option C: OUTER JOIN - An outer join includes unmatched rows from one or both tables but doesn't specifically indicate non-equality. Option D: NATURAL JOIN - A natural join matches columns with the same name in the joined tables, but it is not related to non-equality. So, the correct answer is Option B: NON-EQUIJOIN, as it accurately describes a join based on non-equality of column values in different tables.

In SQL, the command used to change a table's storage characteristics is ALTER TABLE . The ALTER TABLE statement allows you to modify an existing table, which can include changes to the table's structure, storage, or other attributes. Option B: MODIFY TABLE is not a standard SQL command. Option C: CHANGE TABLE is also not a standard SQL command. Option D: "None of these" is incorrect because ALTER TABLE is the correct command for this purpose. So, the correct answer is Option A: ALTER TABLE.

In SQL, the 'AS ' clause is used for renaming columns or tables. It is primarily used for the rename operation . When you use the 'AS' clause, you can give an alias or alternate name to a column or a table, making it more readable or meaningful in the query's result. So, the correct answer is Option B: Rename operation.

The COUNT function in SQL is used to return the number of values within a specified column. It counts the total number of rows in a result-set or the number of non-NULL values in a specific column. Here's an explanation of each option: Option A: values. This is the correct answer. The COUNT function counts the total number of values (or rows) in a result-set or a specific column. Option B: distinct values. The COUNT function can also be used with the DISTINCT keyword to count the number of distinct (unique) values in a column. However, this is not the primary function of the COUNT function. Option C: groups. The COUNT function is not used to count groups. It is primarily used for counting values or rows. Option D: columns. The COUNT function does not count columns. It counts the number of values or rows. So, the correct answer is Option A: values. .

All of the options provided (CHARACTER, NUMERIC, and FLOAT) are valid SQL data types: CHARACTER represents character strings or text. NUMERIC represents numeric values like integers and decimals. FLOAT represents floating-point numbers. So, the correct answer is Option D: All of the above.

NULL in SQL is used to represent missing or unknown data. It is not the same as 0 for integer or blank for character. In fact, NULL is not a specific value, but rather an absence of a value or a placeholder for missing data. So, the correct answer is Option D: not a value.